In general, hearing aid compatibility or HAC is directed to making devices such as telephones, which supply a conventional acoustic signal, compatible for use with devices that assist hearing, such as hearing aids. HAC involves generating a magnetic audio signal (which itself is not audible) from or near the earpiece area of a mobile telephone. The magnetic signal may be generated in addition to or instead of a conventional acoustic audio signal (which is audible). The magnetic signal is received by a receiving coil within the hearing aid. The receiving coil may be a telecoil (or T-coil). The hearing aid converts the magnetic signal received by the receiving coil into an acoustic signal. This acoustic signal, when emitted in the ear channel of a user, allows a hearing aid wearer to hear audio output from the telephone.